Stabilized photographic silver halide emulsions



STABILIZED PHOTOGRAPHIC SILVER HALIDE EMULSIONS James A. Van Allan, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Application November 6, 1956 Serial No. 620,598

13 Claims. (Cl. 96-67) This invention relates to fog-inhibiting agents and stabilizers for photographic emulsions, and to photographic emulsions containing them.

It is well known that photographic emulsions on storage tend to lose sensitivity and to become spontaneously developable without exposure to light. There is normally a detectable amount of the silver salt reduced during development in the areas where no exposure was given; this is commonly called fog, and sometimes called chemical fog where it is necessary to distinguish between it and the effects of accidental exposure to radiation; in this invention, I am not concerned with the latter.

Fog depends both on the emulsion and the conditions of development; for a given emulsion it increases with the degree of development. With constant development conditions, it tends to increase with time, temperature and relative humidity of storage conditions; it is common practice to make accelerated tests of the stability of photographic emulsions by storage at increased temperature or humidity, or both. It is, of course, desirable to have emulsions as stable as possible under the conditions of high temperature and humidity which may occur in tropical climates, for example. Fog usually appears over the whole area of the sensitive coating, but when severe, it frequently is non-uniform. Fog may also be caused by exposure to chemicals, for example, hydrogen sulfide and other reactive sulfur compounds, hydrogen peroxide vapor, and strongly reducing materials. While antifoggants and stabilizers may protect, to some extent, against such effects, it is normally understood that an antifoggant protects against spontaneous growth of fog during prolonged storage or storage at high temperatures and humidities, or during development to maximum contrast and speed, or both.

It is, accordingly, an object of my invention to provide a method for stabilizing photographic emulsions. A further object is to maintain the sensitivity and fog of silver halide emulsions at or close to initial optimum values under keeping conditions of high temperature and humidity. A further object is to provide photographic silver halide emulsions containing antifoggants or stabilizers. Still another object is to provide new chemical compounds and methods for making such compounds. Other objects will become apparent from a consideration of the following description and examples.

According to my invention, photographic silver halide emulsions are stabilized by incorporating therein a compound selected from those represented by the following general formula:

wherein D represents the atoms necessary to complete a benzene ring (which can have substituted thereon substituents, such as methyl, ethyl, chlorine, bromine, hydroxyl, methoxyl, ethoxyl, amino, etc.), X represents a sulfur atom, a selenium atom or a NH group, and Q represents a nitrogen atom or a -CR=; group wherein R represents a hydrogen atom, an alkyl group (e.g., methyl, ethyl, propyl, isopropyl, butyl, etc.), an aryl group (e.g., phenyl, hydroxyphenyl; sulfophenyl, naphthyl, hydroxynaphthyl, hydroxysulfonaphthyl, hydroxysulfophenyl, etc., especially an aryl group containing from 6 to 10 carbon atoms), or an hydroxyl group. The compounds represented by formula I above wherein Q represents a methine group (--CR=) can be quaternated with an alkyl ester;

" such as methyl-p-toluenesulfonate, ethylsulfate, methylsulfate, etc., to provide compounds which, in many instances, have useful stabilizing elfects when incorporated in photographic silver halide emulsions.

The fog inhibitors which I propose to use are added to the emulsion during the process of manufacture, to avoid loss of sensitivity and to inhibit the growth of fog with passage of time under non-ideal conditions of storage.

A solution of the compounds of the invention when added in suitable concentration,before coating, to unsensitized, chemically sensitized, or optically sensitized photographic emulsions does not appreciably afiect the sensitometric values for sensitivity and fog when measurements are made soon after coating. When sensitometric measurements are made at appreciable intervals of time,

at elevated temperatures and dry or somewhat humid conditions these compounds do stabilize photographic speed and maintain fog at a low level.

The preparation of silver halide emulsions involves three separate operations: (1) the emulsification and digestion or ripening of the silver halide, (2) the freeing of the emulsion from excess soluble salts, usually by washing, and (3) the second digestion or after-ripening to obtain increased sensitivity. (Mees The Theory of the Photographic Process (1942).) I prefer to add the foginhibiting agents after the final digestion or after-ripening, although they can advantageously be added prior to digestion.

Listed below are a number of compounds coming within the scope of the above general formula which I have found to be particularly advantageous in practicing my invention. Since the compounds of Formula I wherein R represents an hydroxyl group can be written in their tautomeric form, this possibility has been indicated below. Present evidence indicates that these compounds actually exist in such form (i.e., in their keto form) in the absense of substances tending to accentuate enol tautomerism.

f N l 8-th1a-1,2,3a-triazacyclopent[a]indene 3-methy1-8-thia-1,2,3a-tr1azacycl0pent[a] lndene N N- -C H 3-ethyl-S-thia-I,2,3a-triazaeyclopent[a] indene 3-methyl-1,2,3a,8-tetrazacyclopent[a] indene Patented June 23, 1959 N- -C H 3-ethyl-1,2,3a,8-tetrazacyclopent[alindene (6) (1 ti 1,2,3a,8-tetrazacyclopent[nlindene (7) S N N N- --C H (n) 3-n-pr0pyl-8'thia-1,2,3a-tr1azacyclopent[alindene N NJLC3H70') 3-1s0propy1-8-thia-l,2,3a-triazacyclopent[a]indene (9) z W N -N l S-thia-l,2,3,3a-tetrazacyclopent[alindene (m) g a W N ML- 1,2,3,3a,8-pentazacyc10pent[alindene (n) I N N t 8-se1ena-1,2,3a-triazacyclopent[a]indene S (N N N -O H 3-phenyl-8-thia-1,2,3a-triazacyclopent[a]indene 3-o-hydroxyphenyl-S-thia-l,2,3a-triazacyclopent [a] indene 3- (p-methoxyphenyl -8-thia-1,2,3a-triazacyclopent [a] indene 3- (l-hydroxy-2-naphthyl -8-thia-1,2,3a-triazacyclopent a] 3-1nethy1-S-se1ena-1,2,3a-triazacyc10pent[a]indene The photographic emulsions used in practicing my invention are generally of the developing-out type; also, it is to be understood that photographic emulsions of varying halide content can advantageously be used. The antifoggant compounds used in my invention have been found particularly useful when employed in conjunction with gelatino-silver-bromiodide emulsions, although they can also be advantageously employed for stabilizing other silver halide emulsions, such as gelatino-silver-chloride, bromide, chlorobromide, chlorobromiodide, etc.

The emulsions can also be chemically sensitized by any of the accepted procedures. The emulsions can be digested with naturally active gelatin, or sulfur compounds can be added such as those described in Sheppard US. Patent 1,574,944 and US. Patent 1,623,499, and Sheppard and Brigham US. Patent 2,410,689.

The emulsions can also be treated with salts of the noble metals such as ruthenium, rhodium, palladium, iridium and platinum, all of which belong to group VIII of the periodic table of elements and have an atomic weight greater than 100. Representative compounds are ammonium chloropalladate, potassium chloroplatinate and sodium chloropalladite, which are used for sensitizing in amounts below that which produces any substantial fog inhibition, as described in Smith and Trivelli US, Patent 2,448,060, and as antifoggants in higher amounts, as described in Trivelli and Smith US. Patents 2,566,245 and 2,566,263.

The emulsions can also be chemically sensitized with gold salts as described in Waller and Dodd US. Patent 2,399,083, or stabilized with gold salts as described in Damschroder US. Patent 2,597,856 and Yutzy and Leermakers US Patent 2,597,915. Suitable compounds are potassium chloroaurite, potassium aurithiocyanate, potassium chloroaurate, auric trichloride and 2-aurosulfobenzothiazole methochloride.

The emulsions can also be chemically sensitized with reducing agents such as stannous salts (Carroll US. Patent 2,487,850), polyamines such as diethylene triamine (Lowe and Jones US. Patent 2,518,698), polyamines, such as spermine (Lowe and Allen U.S. Patent 2,521,- 925), or bis-(B-aminoethyl) sulfide and its water-soluble Salts (Lowe and Jones US. Patent 2,521,926).

- The emulsions can also be stabilized with the mercury compounds of Allen, Byers and Murray US. Patent 2,- 728,663, Carroll and Murray US. Patent 2,728,664, and Leubner and Murray U.S. Patent 2,728,665.

The stabilizing combinations of oxadiazoles are eifective in the presence or absence of optical sensitizing dyes. Since optical sensitizing may affect stability of emulsions with respect to sensitivity, fog and latent image changes, the action of the compounds of this invention is not completely independent of optical sensitizing or other emulsion variables. I have found, however, that both un-sensitized emulsions and emulsions sensitized with cyanine or merocyanine dyes, or both, can be treated with pentEa] indenes according to my invention.

The antifoggant and/ or stabilizing action was determined by incubation of the emulsions for one or two weeks at a temperature of 120 F. and constant relative humidity (obtained by placing the emulsions in closed containers, the ambient temperature being about 70 F. and relative humidity about 50-55 percent prior to sealing the containers).

The efliciency of the various antifoggants was determined by measuring the speed, gamma and fog of the incubated emulsions containing an antifoggant and comparing these measurements with those of the same batch Grams N-methyl-p-aminophenol sulfate 2.5 Hydroquinone 2.5 Sodium sulfite 30.0 Sodium metaborate 10.0

Potassium bromide 0.5

Water to make 1 liter.

The speed (BO/E), gamma and fog for each of the emulsion coatings were then measured as indicated above. The results obtained are given in the following table.

6 The speed figures given in the following table are on a logarithmic scale, obtained by the formula: 100 (l -Log E), where E is the exposure in meter-candle-seconds of sunlight quantity radiation required to produce a density of 0.30 above fog. The results obtained are given in the following table.

TABLE II Compound Fresh Tests Incubation Example (g./m0le AgX) Speed Gamma Fog Speed Gamma Fog (a) Control. 312 1. 21 14 314 1. 26 25 (b) 7 (3) 297 1. 07 14 295 95 13 {(0) Control--- 302 1. 17 16 289 83 31 (b) (.3) 307 1. 24 16 290 1. 02 27 {(11) Control- 312 1. 21 14 314 1. 26 25 (b) (3.0) 302 1. 25 12 307 1. 40 14 {(11) Control- 314 1. 30 14 290 1. 19 33 (b) 16 (.3) 250 1. 28 14 244 1. 33 14 {(0) OontroL 312 1. 21 14 314 1. 26 25 (b) 20 (3.0)---- 306 92 12 321 1. 13 20 {(a) Control- 309 1. 32 18 290 1. 05 24 (b) 19 (.03) 308 1. 47 15 299 1.14 16 As mentioned above, the alkyl salts of the compounds of Formula I can also be used to stabilize photographic silver halide emulsions. The data in the following table were obtained exactly as that of Tables I and II, except that salts of the compounds of Formula I were employed instead of such compounds per se. The particular salts employed in the following examples were the methylp-toluenesulfonates. The speed figures are on the same basis of those of Table II. By alkyl salts it is to be understood that I mean alkyl quaternary salts.

TABLE III Salt of Fresh Tests Incubation Example compound .mole AgX) Speed Gamma Fog Speed Gamma Fog Control.-. 305 1. 11 10 297 95 18 2 315 1.09 .11 311 .97 .13 Control--. 310 1.06 .13 294 .95 .23 4 (3.0) 306 1. 04 .13 284 .97 .17

In a manner similar to that illustrated in the above examples, other compounds selected from those represented by the above general Formula I can be incorporated in photographic emulsions for the purpose of stabiliz- TABLE I Fresh Tests Incubation Example (7omlpogndx) mo 9 g g Speed Gamma Fog Speed Gamma Fog 1 a) 5,100 1.20 .10 2, 350 .95 .32 b) 6, 150 1. 21 1a 3, 950 95 1s 2 5 5,150 1.02 .10 4,450 1.00 .28 (b) 5, 000 90 14 5, 700 1. 04 19 3 71) 5,700 1.24 .14 3, 950 1.04 .22 b) 4,150 1.15 11 3,850 1. 07 15 4 5 5,700 1.24 1.4 s, 950 1.04 .22 4,050 1.08 .14 4, 550 1. 05 17 (I 5 5% 5, 000 1. 30 1.3 4, 550 1.07 .10 a 6 4,450 1.03 .11 3,500 1.10 .15 a) 7 2,800 1.29 .11 2, 350 1.34 .15 8 5,850 1.10 .15 3,850 .94 .25 2, 000 .94 .12 1, 050 1. 02 .20 9 2,400 .93 .12 1,040 .97 .15 10{ 5,100 1. 20 15 2, 350 .95 .32 a, 300 1. as 11 2, 950 1. 00 15 11 0, 900 1. 17 17 5, 950 1. 02 .30 5, 550 1. 20 .10 4, 550 1.19 17 In exactly the manner indicated above for the coatings of Table I, a series of tests were made using high speed, negative-type silver bromtiodide emulsions, and these ation. The fog-inhibiting agents useful in practicing my invention can be used in various kinds of photographic emulsions. In addition to being useful in ordinary noncoatings were processed exactly as those of Table I. sensitized emulsions, they can also be used in orthochromatic, panchromatic and X-ray emulsions. If used with sensitizing dyes, they can be added to the emulsion before or after the dyes are added. Suitable dispersing agents for the silver halide emulsions stabilized according to my invention comprise gelatin, or other colloids, such as collodion, albumen, cellulose organic derivatives, synthetic resins, etc.

The optimum amount of fog-inhibiting agent can be determined by making the customary tests employed in emulsion making. Of course, the optimum amount for a given emulsion will vary depending on the presence of emulsion 'addenda, such as chemical sensitizers, etc. In general, I have found that from 0.001 to 5.0 g. of foginhibiting agent per mole of silver halide is sufficient for the purposes of my invention.

Instead of adding the fog-inhibiting agent directly to the photographic emulsion, it is sometimes desirable to incorporate the fog-inhibiting agent in a separate layer which is placed in contact with the silver halide emulsion layer which is to be stabilized. Under such conditions, of course, it is advisable to use a higher concentration of fog-inhibiting agent than indicated above. The antifoggants of our invention function advantageously in acid or alkaline photographic silver halide emulsions.

The compounds selected from those represented by Formula I above wherein Q represents CR: group and R represents a hydrogen atom or a lower alkyl group can advantageously be prepared by condensing a compound selected from those represented by the following general formula:

X TNHNH;

wherein X and D each have the values given above with an orthoester selected from those represented by the following general formula:

wherein R represents a hydrogen atom or a lower alkyl group, such as methyl, ethyl, etc. and R represents a lower alkyl group, such as methyl, ethyl, etc. This method can be summarized as follows:

Procedure A.A mixture of 0.1 mol. of the heterocyclic hydrazine (Formula II) and 0.11 mol. of the orthoester (Formula III) in 60 ml. of xylene was refiuxed for 3 to 4 hours in a flask surmounted with an efficient fractionating column. The alcohol which was formed was continuously removed. When the theoretical amount of alcohol (0.3 mol.) had been collected, the reaction was considered to be complete.

The compounds of Formula I wherein R represents a higher alkyl group or an alkyl group containing a substituent, such as chlorine, carboxyl, etc, can advantageously be prepared by condensing the compound selected from those represented by Formula II above with an acid selected from those represented by the following general formula:

IV. R COOH wherein R represents a higher alkyl group, such as butyl, amyl, etc., or a substituted alkyl group, such as B-carboxyethyl, 'y-hydroxylpropyl, etc. The dicarboxylic acids embraced by Formula IV should generally have at least two carbon atoms between the carboxyl groups.

The compounds of Formula I wherein R represents a hydroxyaryl group can advantageously be prepared by condensing a compound selected from those represented by Formula II above with a compound selected from those represented by the following general formula:

v. .c on

c-coong wherein D and R each have the values given above.

This method of preparation can be summarized as follows:

Procedure B.-A mixture of 0.1 molar quantities of the o-hydroxy phenyl ester (Formula V) and of the heterocyclic hydrazines in 50 ml. of 1,2,4-trichlorobenzene was refluxed. The water which was formed distilled over first at 98101 C. The temperature at the still head then rose and phenol distilled over at -l90 C. The reaction was considered complete when the still head temperature was 203 C. Reaction was usually complete in about 2 hours.

The compounds of Formula I wherein R represents a hydroxyl group can be prepared by condensing a compound selected from those represented by Formula II above with a compound selected from those represented by the following general formula:

VI. R4--NCO wherein R represents an aryl group, such as phenol, tolyl, etc. This method can be summarized as follows:

Procedure C.A mixture of 0.1 mole of the isocyanate (Formula VI) and heterocyclic hydrazine in 60 ml. of trichlorobenzene was refluxed for about 2.5 hours. After cooling to room temperature the crystals which had separated were collected by filtration and washed well with benzene and extracted twice with 400 ml. portions of warm 5 percent sodium hydroxide.

The extracts were combined and acidified with acetic acid. The precipitate was collected by filtration and crystallized from a suitable solvent.

The condensation of the compounds of Formula II with those of Formula IV above can be summarized as follows:

Procedure D.The procedure for cyclization with phenol was as follows: The heterocyclic hydrazine and a large excess of the appropriate aliphatic acid (Formula IV) were refluxed two hours, cooled, and the acyl hydrazine collected by filtration. The acyl hydrazine was refluxed 2-20 hours with 2.5 times its weight of phenol and the phenol then removed by steam distillation. The residue was either recrystallized or first distilled in vacuo and then recrystallized.

The compounds of Formula I above wherein Q represents a nitrogen atom were prepared by condensing the heterocyclic hydrazine of Formula II above with nitrous acid. This method can be summarized as follows:

Procedure E.Nitrous acid ring closure: The heterocyclic hydrazine was dissolved in 15 times its weight of 50 percent aqueous acetic acid, the solution cooled, and added the calculated amount of sodium nitrite in a small amount of water. The tetraza compound usually separated at once, but the reaction mixture was allowed to stand in the cold for an hour before collecting the product.

The compounds of Formula I above wherein R represents an aryl group can also be prepared by condensing a compound selected from those represented by the following general formula:

This method vent. In cases where sodium phenoxide is omitted, slightly lower yields of product were obtained.

The following examples will serve to illustrate the methods for preparing certain of the compounds of Formula I.

Example A .8-thia-J ,2,.3a-triazacyclpent [a] indene 2-hydrazinobenzothiazole (10 g., 0.06 mole) in 50 ml. of ethyl orthoformate was refluxed in a ISO-ml. flask surmounted by an eflicient fractionatingycolumn. The alcohol (11 ml.) which formed was fractionated off. The product separated from the reaction mixture on cooling. It was filtered off and recrystallized from vbutanol to give 5 g. of 8-thia-1,2,3a-triazacyclopent[a]indene, M.P. 178 C. Analysis for C H N S. Calcd: -C=54.8; H=2.8; N='24.0. Found: -C=54.8; H=3.1; N=24.0.

It was also found that the use of a large'volume of water was superior to butanol as a solvent. Thus from 20 g. of starting material, 20 g. of product was obtained Example B.3-methyl-8-lhia-1,2,3a-triazacycl0pent [a] indene Procedure 1.-2-hydrazinobenzothiazole (20 g.) in

100 ml. of triethyl orthoacetate were refluxed while continuously removing the alcohol that formed. The re- .action mixture at first became bright red, but on continued reflux, the color changed to light brown.

After abouttwo hours, 16 ml. of ethanol had been-collected. After chilling the precipitate was filtered off and crystallized from .watenthen from butanol to give 13 g. of .product, M.P. 156 ,C. Analysis for C H N S: Calcd:

Example C.-8-thia1,2,3,3a-tetrazacycl0pent [a] indene A-solution of 8 g. (0.05 mole) of 2-hydrazinobenzothiazole in 100 ml. of 50% aqueous acetic acid was cooled in an ice bath and an aqueous solution of 3.5 g. of sodium nitrite added with stirring. After standing overnight in the refrigerator, the yellow solid was collected, washed with water, and recrystallized from ethanol to give 8.5 g. (98%) of product melting at 108-109 C.

Anal. sale. for G7H4N4s Found 0. 47. 7 47. 9 Fr 2. 3 2. 4 N 31. 9 31. 9 s 18.1 17. 7

Example D.3-phenyl-8-thia-I,2,3a-triazacyclopent [a] indene .A'mixtureof 17 g. (0.1 mole) of 2-chlorobenzothiazole, 14 g. (0.1 mole) of benzhydrazide, 12 g. (0.1 mole) of sodium phenoxide, and 50 ml. g. phenol was refluxed 16 hours. The phenol was removed by steam distillation and the solid residue recrystallized from aqueous alcohol to yield -15 g. of product melting at 153-154 C.

Anal. calc. for CuH NaS Found C. 67. 0 66. 9 H 3. 3 3. 6 s 12. 8 13. 1

' '10 Where the sodium phenoxide was omitted from the above reaction, the yield of product was 6-10g.

Example E.3-methyl-1,2,3a,8-tetrazacylopent[alindene A mixture of 16.5 g. of Z-hydrazinobenzimidazole, 19 ml. of triethyl orthoformate in 60 ml. of xylene was-refluxed for ,fourhours. The initially bright magenta. solution turned a light brown and a copious precipitate formed. After cooling the product was filtered off and crystallized twice from butanol to give 16 g. of' product,

M.P. 23l232 C.

Anal. calc. for CQHsNl .Fqund The intermediates selected from those represented by Formula II have been previously described in the prior art. See U.S. Patent No. 2,073,600, issued March 16, 1937. The compounds of Formula II wherein X represents atom were prepared as follows:

2-CHLOROBENZOSELElNAZOIlE 2-HYDRAZINOBENZO SELENAZOLE A mixture of 36 g. (0.167 mole) of 2-chlorobenzoselenazole, 18.5 g. of hydrazine hydrate, and 10 ml. of water was heated on the steam bath for 1 hour. A solid began to separate almost-at once and after chilling the reaction mixture it was collected. Recrystallization from ethanol gave 25 g. of product melting at 226-27 C.

Analysis.-Calcd. for C H N Se: C, 39.6; H, 3.3;N, 19.8. Found: C, 39.7; H, 3.0; N, 20.3.

The alkyl salts of the compound of Formula I can be prepared according to known methods of quaternation, such as by simply heating the compound of Formula I above wherein Q represents a --CR=group with an alkyl salt in an oil bath. Such a general method is shown in Brooker et al. U.S. application Ser. No. 451,062, filed August 19, 1954.

An example illustrating the preparation of .a compound of Formula I above making use of a dicarboxylic acid is as follows:

COMPOUND 21 CHDALI 1,4-bls S-thia-l,2,3a-triazacyclopent [a]-indene-3-yl) butane A mixture of 33 g. (0.2 mole) of 2-hydrazinobenzothiazole and 15 g. (0.1 mole) of adipic acid in ml. of phenol was refluxed 4 hours and the phenol removed by steam distillation. The solid residue was recrystallized, the yield and physical properties being those given in the following table.

The following table summarizes the physical data for a number of compounds obtained according to the general methods illustrated above. The column headed Solvent indicates the medium from which the desired product was crystallized. The column entitled Method refers to the generalprocedureslindicated above.

aearsea TABLE IV Analysis: Oald. Analysis: Found Compound M. P., Method Solvent Yield,

0. Percent C H N O H N E 98 47.7 2. 3 31. 9 47. 9 2. 4 31. 9 A 80 43.1 2. 3 l8. 9 43. 7 2. 3 19.3 F 40 67.0 3.6 12. 8 66. 9 3. 7 l3. 1 B 81 62. 8 3.4 62. 6 3. 6 C 63 50. l 2. 6 50. 2. F 30 64. 2 3. 9 14. 9 68. 9 4. 1 15.4 B 68 68. 0 3. 5 68.3 3.0 A ethanol 70 45. 8 3.0 17. 8 45. 4 2. 8 17.7 300 D dimethylformamide 65 59. 5 4.0 20. 8 58. 7 4. 4 20. 6

What I claim as my invention and desire secured by Letters Patent of the United States is:

1. A photographic silver halide emulsion containing a stabilizer selected from the group consisting of (l) a compound selected from those represented by the following general formula:

fl N a u wherein D represents the atoms necessary to complete a benzene ring, Q represents a member selected from the group consisting of a nitrogen atom and a group wherein R represents a member selected from the group consisting of a hydrogen atom, an alkyl group, an aryl group, and a hydroxyl group, and X represents a member selected from the group consisting of a sulfur atom, a selenium atom and a NH group where Q represents a group and X represents a member selected from the group consisting of a sulfur atom and a selenium atom when Q represents a nitrogen atom, and (2) quoternary salts of the compounds of said general formula when Q representsa group.

2. A photographic gelatino-silver-halide developing-out emulsion containing a compound selected from those represented by the following formula:

emulsion containing a compound selected from those represented by the following general formula:

wherein D represents the atoms necessary to complete a benzene ring and X represents a member selected from the group consisting of a sulfur atom and a selenium atom.

5. A photographic gelatino-silver-halide developing-out emulsion according to claim 4 wherein the silver halide is silver bromiodide.

6. A photographic gelatino-silver-halide developing-out emulsion containing a compound selected from those represented by the following general formula:

wherein D represents the atoms necessary to complete a benzene ring, R represents a lower alkyl group and X represents a member selected from the group consisting of a sulfur atom, a selenium atom and a NH group.

7. A photographic silver halide emulsion containing the compound represented by the following formula:

S N N N 8. A photographic silver halide emulsion containing the compound represented by the following formula:

8 (Ill 9. A photographic gelatino-silver-halide developing-out emulsion containing a compound selected from those represented by the following general formula:

I N l L wherein D represents the atoms necessary to complete a benzene ring, R represents an aryl group containing from 6 to 10 carbon atoms and X represents a member selected from the group consisting of a sulfur atom, a selenium atom and a NH group.

13 10. A photographic silver halide emulsion containing the compound represented by the following formula:

11. A photographic gelatino-silver-halide developing-out emulsion containing a compound selected from those rep resented by the following general formula:

wherein D represents the atoms necessary to complete a benzene ring and X represents a member selected from the group consisting of a sulfur atom, a selenium atom and a NH group.

12. A photographic silver halide emulsion containing the compound represented by the following formula:

s AN (Ill,

13. A photographic element comprising a silver halide emulsion layer and a colloid layer, and incorporated in at least one of said layers, a stabilizer selected from the group consisting of (1) the compound selected from those represented by the following general formula:

14 wherein D represents the atoms necessary to complete a benzene ring, Q represents a member selected from the group consisting of a nitrogen atom and group wherein R represents a member selected from the group consisting of a hydrogen atom, an alkyl group, an aryl group, and a hydroxyl group, and X represents a member selected from the group consisting of a sulfur atom, a selenium atom and a NH group when Q represents a group and X represents a member selected from the group consisting of a sulfur atom and a selenium atom when Q represents a nitrogen atom, and (2) quaternary salts of the compounds of said general formula when Q represents a UNITED STATES PATENT OFFICE Certificate of Correction Patent No. 2,891,862 June 23, 1959 James A. Van Allan It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, lines 37 to 41, compound (11), the right-hand portion of the formula should appear as shown below instead of as in the patentf x in column 8, line 71, for 1.0 mole read -0.1 mole-; column 10, lines 23 and 24, after represents insert a selenium-; column 11, line 42, for where read when' line 50, for quoternary read quaternary-; column 11, lines 60 to 64, the right-hand portion of the formula should read as shown below instead of as in the patent column 12, lines 49 to 53, the formula should appear as shown below instead of as in the patent- Signed and sealed this 16th day of February 1960.

Attest: KARL H. AXLINE, ROBERT C. WATSON, Attesti/ng Oficer. Oowwnissz'oner of Patents. 

1. A PHOTOGRAPHIC SILVER HALIDE EMULSION CONTAINING A STABLIZER SELECTED FROM THE GROUP CONSISTING OF (1) A COMPOUND SELECTED FROM THOSE REPRESENTED BY THE FOLLOWING GENERAL FORMULA: 